Chapter 8

Question 1

Types of energy associated with attraction and repulsions in hydrogen atoms and other molecules

Answer 1

Hydrogen: Repulsive=positive(kinetic and potential-nuclear repulsion)
Attractive=negative(potential-electron nuclei attraction)

Other molcules: Repulsion=positive(kinetic, potential from nuclear repulsion and potential from electron-electron repulsion)
Attractive=Negative(potential from electron-nuclei attraction)

Question 2

How are attraction/repulsion related to stability?

Answer 2

The molecule will be stable if the attractive contribution and greater than the repulsive one

Question 3

Polar Covalent bond

Answer 3

Unequal sharing of bonding pair of electrons between atoms, resulting in uneven distribution charge

Question 4

Bond polarity

Answer 4

A measure of the extent to which bonding electrons are unequally shared due to differences in electronegativity of the bonded atoms

Question 5

Polar bond

Answer 5

A bond with polar negative and positive charges, where the direction of polarity is indicated by an arrow pointed toward the more negative end of the bond. The degree of polarity depends on differences in electronegativity

Question 6

Dipole moment

Answer 6

(u) a measure of polarity of a molecule. If the centers of partial positive and negative charges do not coincide, a molecule is polar and will have permanent dipole moment

Question 7

Electronegativity

Answer 7

(EN)Ability of an atom to attract electrons in a bond to itself. Increases going up and to the right on the periodic table except for noble gases

Question 8

Differences in negativity corresponding to types of bonds

Answer 8

🔼EN2.0>ionic bonds

0.5

Question 9

Absorption of energy by atoms and molecules

Answer 9

Atoms: Atoms absorb radiation if frequency matches 🔼E of electron energy levels

Molecules: Molecules absorb infrared radiation if frequency matches vibrational modes of molecular bonds

Question 10

Allotropes

Answer 10

Different molecular forms of the same element

Question 11

Resonance

Answer 11

When 2 or more equivalent lewis structures can be drawn for one compound

Question 12

formal charge

Answer 12

FC=#VE-((#unshared e- +1/2(number of e- in bonding pairs))

Question 13

How do you choose the best resonance structure?

Answer 13

1. Formal charges are 0

if this isnt possible,

2. Negative charges on the most electronegative element

Question 14

Exceptions to the octet rule

Answer 14

1. Electron deficient molecules(atoms with fewer than 8 electrons)
2. Free radicals: Molecules having an odd number of electrons, very reactive
3. Expanded valence shell: molecules with atoms having more than an octet, possible if atomic number is >12 and an atom is bonded to a strong electronegative element, decreases formal charge on central atom

Question 15

What does bond length depend on?

Answer 15

Identity of atoms and number of atoms

Question 16

Bond energy and energy involved in breaking/forming bonds

Answer 16

The energy needed to break one mole of covalent bonds in a gas phase. Breaking bonds consumes energy, forming them releases energy

Question 17

Valence shell electron pair repulsion theory

Answer 17

(VESPR) a model predicting the arrangement of valence electron pairs around a central atom minimizes repulsion to produce the lowest energy orientation

Question 18

Steric number

Answer 18

(SN) (number of atoms bonded to central atom)+(number of lone pairs on central atom)

Question 19

Steric number meanings

Answer 19

2=linear
3=trigonal planar
4=tetrahedral
5=trigonal bipyramidal
6=octahedral